flow_dissector: Use IPv6 flow label in flow_dissector

This patch implements the receive side to support RFC 6438 which is to
use the flow label as an ECMP hash. If an IPv6 flow label is set
in a packet we can use this as input for computing an L4-hash. There
should be no need to parse any transport headers in this case.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 17 insertions, 0 deletions

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 62d1cb624f53..c5f3912dad4c 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -80,6 +80,8 @@ ip:
         case htons(ETH_P_IPV6): {
                 const struct ipv6hdr *iph;
                 struct ipv6hdr _iph;
+                __be32 flow_label;
+
 ipv6:
                 iph = skb_header_pointer(skb, nhoff, sizeof(_iph), &_iph);
                 if (!iph)
@@ -89,6 +91,21 @@ ipv6:
                 flow->src = (__force __be32)ipv6_addr_hash(&iph->saddr);
                 flow->dst = (__force __be32)ipv6_addr_hash(&iph->daddr);
                 nhoff += sizeof(struct ipv6hdr);
+
+                flow_label = ip6_flowlabel(iph);
+                if (flow_label) {
+                        /* Awesome, IPv6 packet has a flow label so we can
+                         * use that to represent the ports without any
+                         * further dissection.
+                         */
+                        flow->n_proto = proto;
+                        flow->ip_proto = ip_proto;
+                        flow->ports = flow_label;
+                        flow->thoff = (u16)nhoff;
+
+                        return true;
+                }
+
                 break;
         }
         case htons(ETH_P_8021AD):